The present invention relates to a method for manufacturing a sheet-formed buffer material using gelled material, mainly silicone gel.
A gelled material represented by silicone gel can be expected to serve as a buffer material due to its liquid propagation characteristic as disclosed in the U.S. Patent Application Ser. No. 814726 filed on Dec. 30, 1985, now abandoned.
Such silicone gel, however, has a penetration value of approximately 50 to 200 which has been measured according to JIS (Japanese Industrial Standard) K 2530--1976--(50g load) and therefore it has the feature that the adhesiveness of the surface is high and the tensile strength and the surface hardness of this type of gelled material is weak.
To solve this problem, a buffer material using this type of gelled material as a buffer layer is made by covering the whole external surface of gelled material with a cloth or, if the gelled material is silicone gel, the buffer material is made by causing a hardened layer to be formed on its external surface through a chemical reaction.
The conventional buffer material as described above has accompanied problems in that the whole single buffer layer is deformed during absorption of external shock since the buffer layer made of gelled material is made as single layer and, if this buffer material is used in, for example, a shoe sole, the whole buffer layer causes transversal slipping and therefore the buffer layer cannot exhibit a satisfactory buffering performance.
To solve such problems, it is preferable to finely divide the buffer layer made of a buffer material into a number of separate independent cells so that individual independent cells can independently provide a buffering action and therefore the single buffer layer made of gelled material included in the buffer material need be divided into arrays of independent cells.
As such division cannot be realized on the buffer material on which the hardened layer is formed on the surface of gelled material as described above, a sewing means such as quilting should be used for a buffer material using a cloth as an external covering material as described above.
As described above, however, this type of gelled material, particularly, silicone gel with the penetration value of approximately 150, which is the most desirable material, has a high adhesiveness and, if such material is handled by the sewing means, silicone gel which adheres to the sewing needle may lower the processing speed or may be carried away from the external covering sheet to stick to the surface of the external covering sheet or neighboring object.